Tactus is what some might consider to be a Pixie since he indulges heavily in Pinks, drugs and partying.
During the institute he teamed up with Darrow to take down Mustang and House Minerva. During the escape of House Diana from House Minerva it is believed that Tactus cut underneath the saddle of the Primus Tamara, causing her to fall of the horse during her escape and get trampled to death.
After Tactus joins the Darrow and Mustang's army and they take the castle of House Ceres, Tactus attempts to rape a Ceres slave during the night. He is caught by Milia causing the army to be split, half wanting to defend Tactus as they are part of his house and the other half calling for justice.
Darrow whips Tactus 20 times in front of the army, not holding back causing Pax to nearly hack down Diana soldiers from running to his defense.
After Darrow finishes the punishment, he passes the whip to Tactus and tells him to whip him. Tactus is told to whip him 25 times in front of everybody, explaining that it is also his fault that Tactus committed the crime in the first place. But after 5 lashes, Tactus refused to do anymore. Darrow then makes Pax do it instead, for another 25 lashes. Though traumatic for all involved, Darrow is able to earn Tactus' loyalty and obedience.
Tactus served under his fleet commander Darrow, though his loyalty appears to waver after Darrow's loss to Karnus au Bellona at the Academy and subsequent publicized beating by members of the Bellona family, as well as Tactus's own impending personal danger upon losing his contract to House Augustus. Shortly after Darrow's men abduct Lysander au Lune from The Sovereign, he deserts Darrow and brings Lysander back to The Sovereign in the hopes of getting her favour and protection.
Later, as Darrow recruits Lorn au Arcos to his cause, Tactus arrives with Aja Au Grimmus. Tactus is wounded by a trap set by Darrow, and under orders from Octavia Au Lune, moves to slaughter Lorn's family. Darrow appeals to Tactus and, realizing that there is some good in Tactus and also that he hasn't placed enough trust in his friends, persuades him to return. Tactus breaks down emotionally and accepts Darrow's offer, only for Lorn au Arcos to execute him immediately for endangering his family.